Middle distillate fuel oil compositions having improved pumpability

ABSTRACT

Fuel oil compositions, containing a pour depressant to provide a pour point below 0* F., exhibit improved pumpability as a result of the inclusion of a minor amount of certain low molecular weight butene polymers.

D United States Patent [191 [111 3,838,990 Mievilie Oct. 1, 1974 [54] MHDDLE DISTILLATE FUEL 01L 2,379,728 7/l945 Lieber et al. 44/62 COMPOSITIONS HAVIING IMPROVED un e e a.... PUMPABILITY 3,502,45l 3/1970 Moore et al. 44/58 Inventor: Rodney L. Mieville, Evanston, Ill. Assigneez Standard Oil Company, Chicago, Ill.

Filed: Jan. 18, 1971 Appl. No.: 107,508

Related US. Application Data Continuation-in-part of Ser. No. 770,079, Oct. 23, 1968, abandoned.

US. Cl 44/62, 44/70, 44/80 Int. Cl (31011 11/18 Field of Search 44/62, 80, 70

References Cited UNITED STATES PATENTS 7/1936 Howard 44/62 Primary Examiner-Daniel E. Wyman Assistant Examiner-Mrs. Y. H. Smith Attorney, Agent, or FirmPhilip ll-lill; Arthur G. Gilkes; William T. McClain 5 7 ABSTRACT Fuel oil compositions, containing a pour depressant to provide a pour point below 0F., exhibit improved pumpability as a result of the inclusion of a minor amount of certain low molecular weight butene polymers.

4 Claims, No Drawings MIDDLE DISTILLATE FUEL OIL COMPOSITIONS HAVING IMPROVED PUMPABILITY CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 770,079 filed Oct. 23, 1968 now abandoned.

BACKGROUND OF THE INVENTION In the storage and use of heavy and middle distillate fuel oils, problems connected with pour points are familiar to the art. The pour point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbance under specified conditions. Pour point problems arise through the formation of solid or semi-solid waxy particles within an oil composition. For example, in the storage of fuel oils (e.g., heater oil and furnace oil) or diesel oil during the winter months, temperatures frequently are in the range of l to F. These low temperatures often cause crystallization or solidification of wax in the distillate oil.

One solution to the problem of handling oils below their natural pour point is to incorporate in the oil composition one of a wide number of known pour point depressants. In this manner it is possible to maintain flowability in a fuel even at very cold temperatures. It has been discovered, however, that pour point depressants alone are often not sufficient to permit effective handling of fuel oils at cold temperatures. This is because all hydrocarbon fuels yield crystals of solid wax as their temperature is lowered beyond the cloud point, which is defined as the temperature at which paraffin wax or other solid substances begin to crystallize out or separate from solution when the oil is chilled under definite conditions (ASTM D 97). In many cases, even in the presence of a pour point depressant, the crystals which form are sufficiently dense so that an immobile layer of crystals is formed in the bottom of storage tanks and tends severly to clog pumps, filters and screens. Unfortunately, most pour point depressants tailored for middle distillate fuels are not effective in inhibiting such crystal growth or in modifying it in such a way as to maintain pumping capacity in the oil.

It has additionally been discovered that pumpability problems in some fuels are especially severe around the cloud point. Thus a fuel may exhibit workable pumpability at very low temperatures while being virtually non-pumpable in the warmer cloud point range.

SUMMARY OF THE INVENTION This invention relates to fuel oil compositions having improved pumpability characteristics. More particularly, this invention relates to improving the pumpability of fuel oils which have already been modified to exhibit depressed pour points.

I have now discovered that certain relatively low molecular weight polybutenes, when incorporated in pourdepressed middle distillate fuel compositions at a concentration ranging from 0.005 to 0.05 weight percent, are effective in maintaining pumpability in the fuels at low temperatures and are especially effective in maintaining pumpability at or near the cloud point of the fuel.

The polybutenes of this invention are viscous liquids obtained by polymerization of C olefins, singly or in combination, in the presence of a Friedel-Crafts catalyst system. The liquid polymers have a number average molecular weight within the range from about 300 to about 3,000.

DESCRIPTION OF THE INVENTION The middle distillate oils with which my invention is concerned may generally be described as distillates boiling in the range from 350 to 750F. and already modified to exhibit depressed pour points below 0F. These distillates may comprise virgin oils or cracked stocks derived, for example, from cycle oils boiling higher then gasoline. Examples of distillates suitable for use in this invention include diesel fuel (ASTM D975), jet fuel, fuel oils (ASTM D 396), gas oils and the like. Of course, suitable distillates may additionally contain additives such as rust inhibitors, corrosion inhibitors, anti-oxidants and similar agents designed to impart a specific property to the oil.

Pour point depressants suitable for modifying the middle distillates with which this invention is concerned, include any effective pour depressant known to the art. For example, such depressants may be ethylene/propylene,

The low molecular weight polybutenes which I have discovered impart excellent pumpability to pourdepressed middle distillate fuel compositions, especially at or near the cloud point, have an average molecular weight in the range from about 300 to about 3,000. These polybutenes are viscous liquids generally prepared by the polymerization of l-butene, 2-butene and isobutene, either singly or in combination, in the presence of AlCl as catalyst.

To achieve satisfactory pumpability in difficultlypumpable fuel compositions as described above I have found it necessary to employ a minimum of about 0.005 weight percent of the described polybutene additives. In general, the polybutenes may be employed in amounts ranging from 0.005 to 0.05 weight percent, with 0.01 weight percent being a preferred amount.

I have further discovered that when a polybutene additive having a number average molecular weight of about 900 is employed together with an ethylene/acrylic ester/propylene terpolymer pour point depressant in a weight ratio of about 1:10, a synergism exists which results in a dramatic increase in the pumpability of the fuel composition.

EMBODIMENTS OF THE INVENTION To illustrate the effectiveness of the inclusion of the described polybutenes in middle distillate fuel compositions, pumpability tests were run on No. 2 fuel oils containing pour point depressants. The pumpability test employed is designed to simulate actual fuel handling conditions and is described as follows:

A tape wrapped 500 ml. leveling; bulb is fitted in the top with a 3-way stopcock which is wired on. The bottom of the bulb is connected by a short strip of rubber tubing to the bottom of a J-shaped piece of 3/16 inch copper tubing 14 inches long. The top of the copper tubing is fitted with a brass union containing a 30-mesh screen soldered into a brass washer having a 15/32 inch opening. The level of the screen is at about the same height as the stopcock on the leveling bulb. A 250 ml. buret is connected to the brass union by rubber tubing.

To perform a test with this equipment, a 300 ml. fuel sample is poured into the leveling bulb and, with the stopcock open, is subjected to one of the cooling sequences shown in Table 1. When cooling is complete, a nitrogen pressure of 15 p.s.i.g. is introduced through the stopcock. A pumpability reading is obtained by measuring the delivery time in seconds between the and 200 ml. marks on the measuring buret.

T Specification Temperature EXAMPLE 1 The pumpability ofa No. 2 fuel oil having the following specifications,

Pour point, F. 20 Gravity, AP1 32 Distillation. F.

was determined by the procedure described above for 20F specification temperature. The fuel had been modified to exhibit a depressed pour point of -20F by the inclusion of 0.04 weight percent of an ethylene/a- Composition Pumpability (20F.)

No. 2 fuel +0.04% pour depressant Plugged. no flow No. 2 fuel +0.04% pour depressant +0.01% H-300 200 ml./6 seconds No. 2 fuel! +0.04% pour depressant +0.01% H-l500 200 ml./6 seconds EXAMPLE ll The pumpability of three No. 2 fuel oil compositions,

modified with terpolymer to exhibit depressed pour points, was determined at -5F. and 12F. to demonstrate the special pumpability problems often observable near the cloud point of an oil. Fuel A had the following specifications:

Pour point. F. Cloud point. F. 0 Gravity. AP1 34.8

Fuel B had the following specifications:

Pour point F. Cloud point. F. 2 Gravity. AP1 33.8

Fuel C had the following specifications:

Pour point, F. 25 Cloud point, F. 0 Gravity, APl 34.0

All three fuels were modified to depress the pour point by the addition of 0.04 wt. percent of an ethylene/acrylic ester/propylene terpolymer. Pumpability was also determined at 5F. after adding additionally 0.01 weight percent polybutene.

It appears clearly from the following table that although none of the three oils was pumpable at 5F in the absence of the polybutene additive, all three oils were pumpable at that temperature when 0.01 weight percent of a polybutene having an average molecular weight of about 900 was included in the formulation.

Fuel Sample Pumpability Pumpability Pumpability at 5F.

Test at 5F. Test at 12F. with 0.01 wt. 7:

polybutene (MW 900) Fuel A 0 ml./ sec. 200 ml./24 sec. 200 ml./9 sec. (cloud point 0F.) Fuel B 0 ml./60 sec. 200 ml./14 sec. 200 ml./5 sec. (cloud point +2F.) Fuel C 0 m1./60 sec. 200 m1./15 sec. 200 ml./8 sec.

(cloud point EXAMPLE in To illustrate the synergistic effect between the polybutene additives of this invention and an ethylene/acrylic ester/propylene terpolymer, used as a pour point depressant, pumpabilities were determined at -30F. in No. 2 fuel oil compositions containing each additive singly and in combination. The results below show a striking increase in pumpability when the polybutene was employed together with the terpolymer pour depressant.

1. A distillate fuel composition, having improved pumpability performance at temperatures below F, comprising: (a) a middle distillate fuel oil having a pour point below 0F, said pour point having been decreased below 0F by the addition to the fuel oil of a sufficient amount of an ethylene-acrylic ester-propylene terpolymer effective therefor, and (b) from about 0.005 to about 0.05 weight percent of a polybutene, said polybutene having a number average molecular weight within the range from about 300 to about 3,000.

2. The composition of claim 1 wherein the amount of polybutene in the middle distillate fuel oil is about 0.0] weight percent.

3. The composition of claim 1 wherein the number average molecular weight of the polybutene is within the range from about 900 to about 1,200.

4. The composition of claim 1 wherein the polybutene has a number average molecular weight of about 900, the weight ratio of terpolymer to polybutene being about 10:1. 

1. A DISTILLATE FLUEL COMPOSITION, HAVING IMPROVED PUMPABILITY PERFORMANCE AT TEMPERAUTRES BELOW 0*F, COMPRISING: (A) A MIDDLE DISTILLATE FLUEL OIL HAVING A POUR POINT BELOW 0*F, SAID POUR POINT HAVING BEEN DECREASED BELOW 0* BY THE ADDITION OF THE FUEL OIL IF A SUFFICIENT AMOUNT OF AN ETHYLENE-ACRYLIC ESTER-PROPYLENE TERPOLYMER EFFECTIVE THEREFOR, AND (B) FROM ABOUT 0.005 TO 0.05 WEIGHT PERCENT OF A POLYBUTENE, SAID POLYBUTENE HAVING A NUMBER AVERAGE MOLECULAR WEIGHT WITHIN THE RANGE FROM ABOUT 300 TO ABOUT 3,000.
 2. The composition of claim 1 wherein the amount of polybutene in the middle distillate fuel oil is about 0.01 weight percent.
 3. The composition of claim 1 wherein the number average molecular weight of the polybutene is within the range from about 900 to about 1,200.
 4. The composition of claim 1 wherein the polybutene has a number average molecular weight of about 900, the weight ratio of terpolymer to polybutene being about 10:1. 